Basically large user base mail systems is not hard in theory. The main
thing to do is stop thinking of them as users (in the sense of having
accounts on the server boxes) and purely as mail destinations or
recipients. A recipient has some file space accessible from the
server, but normally will not have a UID or other unix identity.
The user db can be done several ways - LDAP, cdb and DNS are three ways
I have seen.
In general a system of this sort would only use a very small subset of
the available directors - remember you can do *anything* with a
smartuser director and appropriate conditionals. You definitely do
not need the localuser directors, and forwardfile ones would be rare.
Filestore is the biggest problem. You almost certainly need to think
in terms of NAS which restricts things greatly, however the NAS storage
allows spreading of the mail load. An alternative is the IMAP favoured
approach of small IMAP servers and directing users to the apprpriate
one... I have problems with that. Your mailbox storage scheme also
has a lot of bearings here.... cyrus for example will *not* work
reliably over NFS (even with decent locking).
ch4di@??? said:
> very inspiring Yann ... but NOT a bit informative ... i think the
> dood's question was very clear, he/she's looking for some help on how
> can it be done and not some inspiring stories of success abt. someone
> who actually did it.
Frankly I don't generally answer questions of this sort in detail, only
ever sketch out pertinant areas. I am sick and tired of wannabe ISPs
with no clue whatsoever trying to get things set up for them which they
will then break and blame everyone else for. If you are building a
system of this size you need to sit down and bang your head against
some walls until you understand the whole system. If you ain't
prepared to do that then you shouldn't be trying.
If you really want questions on ultra large scale mail systems answered
by other people, then you can always go to one of the few people who
has done that before and pay them consultancy.
[and I have got a number of requests both on and off list basically
wanting me to set up full mail systems for people in my copious spare
time, which I consider to be a complete abuse of what I set the lists
up for]
I, and Yann in my experience, will answer specifics, but big mail
system design depends on the the goals you have for the system and the
constraints. You cannot just start posting recipes for that. [You
can always get clues by seeing what patches/features have come from the
big ISPs over the years]
Nigel.
--
[ - Opinions expressed are personal and may not be shared by VData - ]
[ Nigel Metheringham Nigel.Metheringham@??? ]
[ Phone: +44 1423 850000 Fax +44 1423 858866 ]
